Laser-based coating removal systems use pulses of light from high power lasers to ablate or vaporize the paint or other coating from a surface. Each pulse removes the coating from a small region, typically 0.1 to 100 square mm. The laser is pointed to a different area after each pulse, where the removal process is repeated until the entire surface is cleaned. An advantage of lasers for coating removal is that each laser pulse removes a predictable portion of the thickness of the coating, in the small region impacted by the pulse. This opens the possibility of selective stripping where, for example, the topcoat could be removed but not the primer.
A problem with laser de-coating systems is the possibility of damaging the surface if the stripping process is continued after all the coating is removed. A particular source of the possible damage is the result of overheating the surface due to the absorption of the excess laser light by the surface after the coating has been removed. Previous techniques to overcome this problem have relied on measuring the color of the surface at each point within the laser scan field prior to firing the laser at that point. However, these techniques do not work well if the distance and the angle from the laser optics to the substrate vary widely as is the case in many handheld laser de-coating systems on non-flat surfaces.